Manticore gives STR and VIT bonus, together with 14% Light Defense.
While Apocalypse set gives extra HP / MP bonus. The other bonuses are the same for the two (Final Damage, Patk / Matk). So you figure out for yourself which one would you rather have, stats and Light Defense? Or higher HP/MP? Keep in mind that
STR also increases your Stun and Paralyse, VIT increases your physical defense and HP.

My personal choice is Manticore set for the extra 14% Light Defense. If you only wanna make full use of the HP suffix (eg. heal more HP), then Apocalypse set is the better choice. So you make your own decision.

manticore for a physical type character build, apocalypse for a magical type character build. my opinion only!!
this is why I chose apoc over manti, I don't need the str bonus only the higher hp, even though I'm a sm, more focused on magic though